The LiftMaster K21-10340 115V Transformer is an original LiftMaster replacement component for select commercial door operators. Its job is to convert incoming 115 VAC line power to the low-voltage control power used by the operator’s logic board and connected accessories such as photo eyes, key switches, and receivers. Use this transformer to restore reliable control power when the original unit is damaged or failing, maintain compliance with OEM specifications, and keep commercial overhead door or gate systems operating as designed.
Engineered for North American 115 VAC supply applications, this transformer is intended for use with compatible LiftMaster commercial operators and control systems. For proper fit, match the exact part number K21-10340 to the parts diagram for your specific operator model and serial range. Installation should be performed by a qualified technician following the operator’s service manual, with power disconnected and lockout/tagout procedures observed in accordance with UL 325 and local electrical codes. Correct wiring to the designated terminal points and verification of line voltage are required to ensure safe, dependable operation in commercial environments.